Boffins in Australia have applied a hundreds-of-years-old astronomical rule to data from the Kepler planet-hunting space telescope. They've come to the conclusion that the average star in our galaxy has not one but two Earth-size planets in its "goldilocks" zone where liquid water - and thus, life along Earthly lines - could …

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Obligatory xkcd

Tidal forces required in early evolution

The main argument for the need of a moon that I recall coming across is that tidal forces and flows provide a significant advantage to multicellular organisms over single celled organisms. Being long allows an organism to gain more movement and nutrients from the tidal flows, compared to a single cell creature.

This would create an evolutionary pressure to the more complex life form (which otherwise at this stage would likely fall prey to consumption by the existing simpler single celled lifeforms)

The outcome that has been discussed then is that without a large moon, would you get to multicellular lifeforms? If so what would be the pressure to do so?

Re: Tidal forces required in early evolution

Actually the latest story is that evolutionary experimentation was greatly facilitated by a couple of passages through "snowball earth" type environments where formerly connected environments where disconnected and sealed off for a few 100'000 years, then reconnected as the snowball thawed?

Re: Tidal forces required in early evolution

competition/mutual benefit.

One of the steps in evolution most overlooked is that the eukaryotic cell is actually most likely a symbiont of several separate "ancestor-organisms", of which one, the mitochondrium, even still has its' own DNA and reproduces separately within the cell.

Something along the lines of that mechanism still exists today,where ( very anaerobic) methanobacteria survive in an oxygen environment by living in the creases of the cell walls of E.Coli bacteria, occasionally temporarily being incorporated as "organelles" within the host body itself. ( and giving rise to the rather rare, but fun, "lightable fart". Ain't biology fun.. ;) )

As far as I can remember the biggest influence the moon has on the earth with regards to the "sustainability of life" is that it stabilises the earth's spin with regards to the ecliptic plane, creating an environment that is more stable than it would be without. Then again, we don't see Mars, or any other planet flipping its axis of rotation all around, so ymmv there.

Never been too fond of the tides-enabling-life/driving evolution theory, given that the moon at the crucial time was a lot closer to the earth, and the tides it created were a bit more frequent and.. prominent.. than the gentle stuff the moon gives us nowadays.

Re: Tidal forces required in early evolution

I believe this is fairly common,in fact. Human farts usually contain significant hydrogen and methane. Because hydrogen has a high flame velocity, lighting farts can be very unwise.

It isn't hard to explain why multicellular organisms evolved, as bacteria are often colonial and derive benefit from it (colonies adhere to substrates and their waste products can protect them). Eukaryotic cells can have more specialised organelles than bacteria, making them more efficient predators. Once eukaryotes become colonial, the opportunity and the mechanisms become available for differentiation* to improve the fitness of the colony and bingo, multicellular organisms.

*A sessile eukaryotic colony will have concentration gradients of oxygen, carbon dioxide and waste products. These gradients could act as markers to trigger differentiation.

Re: Tidal forces required in early evolution

A moon stabilizes the axis of rotation of a planet. Without one, the axis of rotation is unstable, and sooner or later will pass through the plane of the planet's orbit (with a timescale of under a million years). That's too fast for the evolution of all but mono-cellular life to adjust to a planet that "suddenly" no longer has a day-night cycle. (ie, one where the whole planetary surface is like our poles: half a year of night, then half a year of day).

Don't know how large a moon is needed, but no moon at all is no good at all.

More than a coincidence?

I didn't think that Titius-Bode sequence was widely accepted as being anything other than a coincidence. But as they are predicting increased planet detection rates based upon using it, then I guess we are about to find out if it has some use.

Re: More than a coincidence?

It has been suggested that Bodes Law arises because of orbital resonances between planets in relatively circular orbits but even in our solar system it fails once you get to Neptune. We already know of solar systems containing large planets in very eccentric orbits which would presumably disrupt any Bodes Law pattern in their system. Hence it seems a bit of a stretch to attempt to calculate the average number of planets in the habital zone using such a law.

Re: More than a coincidence?

Unless new macro-physics exists (i.e. Laurent Nottale has actually something good, not sure whether his stuff makes sense) or there are unexpected effects regarding the final state of an energy-losing system of multiple gravitating bodies (I remember some interesting macro effects in large scale simulations - galaxy sized - which were not readily explained)

Re: More than a coincidence?

The orbit of any planet in a solar system with more than one planet is chaotic. (Mathematical fact, mathematical definition of chaotic). Given infinite time, all but one planet will inevitably be ejected into interstellar space (or less likely swallowed by its sun or collided with another planet).

Fortunately for us, "enough time" for our solar system greatly exceeds the lifetime of Sol. Also the future orbit of Earth can be predicted to remain much as it is today for the next 100My at least, given the accuracy of the best astronomical observations of the rest of the planets in our system and inverse-squares gravitation.

However, in a solar system with a Jupiter-mass planet in a very eccentric orbit, smaller planets would not remain in the Goldilocks zone for the (assumed) billions of years it takes for advanced life to evolve.

Re: More than a coincidence?

"The orbit of any planet in a solar system with more than one planet is chaotic. (Mathematical fact, mathematical definition of chaotic). Given infinite time, all but one planet will inevitably be ejected into interstellar space (or less likely swallowed by its sun or collided with another planet)."

As far as I remember "chaotic" in the mathematical sense does not mean unstable, it means unpredictable. A chaotic system's future state can only be predicted if you know _exactly_ the initial state. A small (infinitesimal) change in initial state leads to a large and undefined change in future state.

Re: More than a coincidence?

"I didn't think that Titius-Bode sequence was widely accepted as being anything other than a coincidence."

I've mentioned this in El Reg comments before when the subject of Bode has come up... but back in the early 1990s I did a maths GCSE for fun (already have an O level from school) and for the coursework I did a ridiculously long thing on Bode's Law - I keep hoping to find the file on one of my computers so I can re-read it, take out anything irrelevant and unnecessary, and throw the rest onto the web. Fat chance, though, because that was a silly number of computers ago - at least, that's what I thought.

I found a 3.5" disc recently with "Bode's Law" written on the label1. :)

Unfortunately, though, while I can read the disc if I drag the right computer down from the loft, what that computer won't be able to do is shove the contents over the network to my current computer(s). Or print it. Or anything useful, really. Still, it's a start. :)

1. Actually, it says "Bodes Law" - well, I was over twenty years younger.

Re: More than a coincidence?

“It could be that there is some other bottleneck for the emergence of life that we haven’t worked out yet. Or intelligent civilisations evolve, but then self-destruct.”

Given that we developed nuclear weapons before any form of space travel, if other civilisations evolved along similar lines, than is it not possible they blew themselves to dust before getting off the ground?

God is actually Cave Johnson

Or they run out of steam before doing anything serious. Space travel is hard.

But this universe seems to be made to order as a petri-dish to run a large-scale experiment about overcoming various obstacles to survival using genetic algorithms evolving from the ground up in a reduced (but with small h-bar) physical setting. If Earth doesn't manage, I am sure others will.

Re: Look for the EMP

Unlike GRBs (gamma-ray bursts). One of those in our galactic neighbourhood could all but sterilize our entire galaxy. We're assuming these are natural phenomena, but are we sure?

And then there's whatever mystery created the "Oh My God" particle (3x10^20 eV, or fifty Joules!). Whatever made it must have been within our galaxy, because its half-life before interaction with a cosmic background microwave photon precludes any extra-galactic origin.

Re: 'Or intelligent civilisations evolve, but then self-destruct'

Goldilocks?

The old woman (not little girl) in an early variation of the story was described at various points in the story as impudent, bad, foul-mouthed, ugly, dirty and a vagrant deserving of a stint in the House of Correction and later is impaled on the steeple of St Paul's Cathedral!

Re: Goldilocks?

Re: Goldilocks?

If the aliens read the Wikipedia article on Goldilocks, especially the "interpretations" section where the psychoanalysts get at it, they would put out warning notices to keep away from such a bonkers civilisation.

Re: Goldilocks? @ravenviz

It's actually Girldie Larks and the Forebears, according to Afferbeck Lauder: Father Behr, Mother Behr, Baby Behr and Cammom Behr. Girldie Larks was a juvile dinquent tea nature, whose career in crime was ended when Cammom Behr cut out her heart and threw it down a well. It's a very popular Furry Tile.

Re: Goldilocks? @ravenviz

Space is big, signals are weak

I would think that all but directional signals specifically sent towards us would be too weak for the SETI to detect and, in any case, high power broadcast signals would probably be used for a very brief period in any civilisation as they quickly move to more efficient low-power directed and coherent beam transmission.

Furthermore, they would probably switch to digital equally quickly and then start encrypting everything routinely, for commercial reasons if not for anything else. And a well encrypted transmission looks pretty much like random noise.

So, the chances that there is a civilisation that is going through their momentary high-power analogue broadcasting phase and that is close enough for us to detect them and is using the frequencies the SETI is listening to are very very slim even if, otherwise, there are millions of inhabited star systems in our galaxy.

Re: Space is big, signals are weak

Re: Space is big, signals are weak

Extremely unlikely. There is no selective pressure to be able to communicate across interstellar distances, but there is plenty of pressure to conserve energy. A species that used radio biologically wouldn't do so at very high power.

Re: Space is big, signals are weak

Furthermore, they would probably switch to digital equally quickly and then start encrypting everything routinely, for commercial reasons if not for anything else. And a well encrypted transmission looks pretty much like random noise.

That's any well-coded signal, ie coded to make efficient use of available bandwidth. The main difference between encryption and "mere" efficient coding, is whether you publish the decoding algorithm and key(s), or not!

Re: When lewis gets back

When lewis gets back

make sure he holds his pen with the same hand he wrote with before he left. Other wise you can assume that ... Hang on there's someone at the door. …. John G Imrie

Knowing something of Lewis’s past history and present circumstance has one thinking of a perfect enough current placement for future deployments of new style 77th Brigade shenanigans/Intelligent Signalling Interdiction Services.

El Reg is certainly no sub-prime operation, is it, and surely a great deal more than just the simple sum of a number of parts.

I think (and hope) the Great Filter lies in our past

It took a billion years for prokaryotes (simple single-celled life) to evolve. Then another 1.6 billion for eukaryotes (more complex, but still single-celled). Then another billion years to get multi-cellular life, and another billion to get primates. We have no idea whether these steps always take that long, or whether we're unusually fast or unusually slow. I find it easy to believe that getting to multi-cellular life usually takes 4 times the 3.6 billion years it took us, in which case it is longer than the age of the universe. In other words, there could be lots of slime out there, but not much intelligent life.

There would still be some intelligent life, but if it's rare, it's probably too far away for us to detect it (or vice versa). I see no reason think whoever is first will have a drive to colonise the galaxy. It might make more sense to upload themselves to virtual reality instead, and have all the space they need. Especially if they've achieved zero population growth (arguably a pre-requisite for a civilisation to survive more than a million years).

Whatever: Fermi's Paradox isn't a paradox. Anyone who understands enough to see why it's an issue should have enough imagination to explain it away.

Finally, the Fermi Paradox mention

Not surprised the original author didn't mention the Fermi Paradox. Same blathering idiot frequently denies climate change, so probably he never heard of Fermi. "Who was Fermi? Another one of those damn fool money-grubbing so-called scientists? Oh, you say he had a Nobel thingee or such?" However, somewhat surprised to see so little mention of the Fermi Paradox here in the comments.

My amplified form is to consider a single stable civilization that started with our level of radio technology within our galaxy. If they wanted to say "hi", they could create a major radio beacon. They don't even need to run it continuously, but just let out a a few megawatts of encoded squawk when they are at their time of low power demand. To define stable, let's say we can claim 5,000 years of civilization, and our "stable civilization" is at least 20 times more stable. Then by now their signal would have reached every corner of our galaxy--and even with our primitive technology, we would have picked it up. Therefore, we can safely say there is no such civilization in our galaxy that wants to say "Hi."

Various resolutions of the Paradox, but the two I favor are:

1. A proclivity for technology is not a survival trait, and all such civilizations quickly exterminate themselves, probably by a cost-effective bio-weapon.

2. Naturally evolved intelligences like humans replace themselves with AIs, and the AIs are talking among themselves in ways we can't perceive. In this case, we can conclude the AIs are not malevolent, or they would have exterminated us by now. I'd prefer to believe they are wagering quatloos on how long we survive or genuinely interested in the various paths taken by natural evolution. However, in any version of this case, I can't imagine they would ever bother talking to us. What would you say to a flea (even if you knew the flea or its ancestors had once created a super-smart dog)?

Lewis has gone out ...

After writing the article he probably headed off to an inter-services meeting to collect and collate story lines for Battalion 77 internet psyops. Pint because that's what's needed to wash away some of the schoolboy nonsense that this topic generates in predictably massive volumes.

I don't think the fact that we haven't detected alien life is puzzling at all. The costs of interstellar travel are such that it's never going to be something done lightly, despite what sci-fi writers seem to think and the signals coming from those planets would be very hard to identify.

Consider this for a second: We've had the technology, or at least the theory for it and capability to build for those theories, needed to build successful a generational ship for interstellar travel for 50 years now (the key technologies being the Orion drive and the O'Neill cylinder) and no ones even considered doing it because it would be ludicrously expensive. When you start talking about ships that could make the trips in sane time frames the costs get even higher thanks to the absolutely absurd energy requirements (not to mention disastrous side effects like causing gamma ray bursts).

As for the signals, we actually do have one or two signals we've picked up that could potentially have come from alien radio telescopes, but identifying them as such with any certainty is basically impossible.

Basically I don't believe we'll ever visit other stars until Earth is in danger of being destroyed, and then I think we'll do it once and only once. The only way around it is if we somehow figure out how to make stable wormholes, but I've doubts about that to.

We won't ever do interstellar travel as biological human beings. The speed of light and the vulnerability of mammalian life to interstellar radiation guarantee this.

However, AI or human uploads into Silicon might not be so constrained. They can be radiation-hardened, and can slow down their clock-rate to make the subjective speed of light seem faster by orders of magnitude.

It's also possible that other forms of bio-life might evolve with a slower and less radiation-sensitive chemistry. Some trees live 3000+ years. There's a fungus in the USA that's at least 100,000 years old (also the largest, most massive life-form yet discovered on Earth). Perhaps elsewhere, there are intelligences that live for many My, for whom a 30ky interstellar journey wouldn't seem impossible.

But back to the Fermi paradox - where are they? (Just possibly: out in our Oort cloud, living slowly and quietly. Or here on Terra: we call them fungi, they think too slowly for us to consider them sentient. When they get around to noticing us, they might decide we're a plague and do something about it ...).

Do you know how the aliens got here?

What aliens would say to us if they could

Among the many theories proposed as to why aliens aren't communicating with us, one of the most disturbing is that if they could, what they would say to us is:

"Shut up, you fools!"

We're like a lost fawn bleating in the forest for its mother. We're likely to attract the attention of whatever it is that has everyone else staying quiet and hiding. That's why there has been some criticism of certain experiments attempting to broadcast from earth to other potentially-inhabited star systems. Is it worth taking the chance? Do you want someone else taking that chance on behalf of all of us?

or maybe...

A.I.

Many civilizations were probably taken over by their own, or an invasive Artificial Intelligence. If that is the case, we will not detect them, they will just sit dormant and listening until they pick up a signal from us, then they will deide our fate in a microsecond.